Modeling Transient Wellbore Behavior and Near-Wellbore Damage During Carbon-Dioxide Injection in Depleted Gas Reservoirs

ABSTRACT: In this paper we describe a study focused on modeling the dynamic wellbore behavior and assessing completion and near-wellbore damage in the context of carbon dioxide (CO2) injection to depleted gas reservoirs. The results of the multiphase flow simulator in terms of pressure and temperature distributions along the well for various timesteps have been used as boundary conditions of the dynamic reservoir simulator. The reservoir model considers a near-wellbore region fully saturated in CO2. Thermal-hydraulic-mechanical (THM) coupling for completion and surrounding rock has been enabled, linking the reservoir simulator to the geomechanical simulator. A simple staggered coupling scheme also called one-way coupling (OWC) has been used to describe the behavior of the host rock and completion and evaluate potential damage during simulated injection scenarios. The results enable us to investigate the influence of various parameters, with the objective of supporting the design of carbon capture and storage (CCS) injection wells and materials, plus the definition of procedures that can reduce the risks associated with thermal shock. 1. INTRODUCTION CO2 sequestration has emerged as a promising strategy to mitigate greenhouse gas emissions and play a part in climate change control by safely injecting significant quantities of CO2 deep underground, while ensuring permanent containment integrity. During injection, temperature and pressure changes within the wellbore and its vicinity impact completion equipment, tubulars including casing and liners, annular fluids, cement, and subsurface formations. Extreme temperature variations may also alter rock properties and fluid behavior. These thermal and pressure variations can affect injectivity and will induce mechanical stresses within the well system, cement, and surrounding rocks; Oldenburg (2006), Pekot et al. (2011). Understanding these effects is crucial for assessing and ensuring the integrity of the well, host rock, and seals, while minimizing or eliminating formation damage and optimizing CO2 injection strategies. For seabed temperatures ranging between 5 to 15°C the CO2 is in liquid phase and denser. Transportation of liquid CO2 is a favored option for many offshore projects. Similar considerations may apply to the well completion, where the injection of a denser fluid reduces tubing head pressure and tubing size requirements.